1 /* 2 * Copyright (c) 1982, 1986, 1988, 1990 Regents of the University of California. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * from: @(#)tcp_timer.c 7.18 (Berkeley) 6/28/90 34 * $Id: tcp_timer.c,v 1.6 1994/01/08 23:07:22 mycroft Exp $ 35 */ 36 37 #include <sys/param.h> 38 #include <sys/systm.h> 39 #include <sys/malloc.h> 40 #include <sys/mbuf.h> 41 #include <sys/socket.h> 42 #include <sys/socketvar.h> 43 #include <sys/protosw.h> 44 #include <sys/errno.h> 45 46 #include <net/if.h> 47 #include <net/route.h> 48 49 #include <netinet/in.h> 50 #include <netinet/in_systm.h> 51 #include <netinet/ip.h> 52 #include <netinet/in_pcb.h> 53 #include <netinet/ip_var.h> 54 #include <netinet/tcp.h> 55 #include <netinet/tcp_fsm.h> 56 #include <netinet/tcp_seq.h> 57 #include <netinet/tcp_timer.h> 58 #include <netinet/tcp_var.h> 59 #include <netinet/tcpip.h> 60 61 int tcp_keepidle = TCPTV_KEEP_IDLE; 62 int tcp_keepintvl = TCPTV_KEEPINTVL; 63 int tcp_maxidle; 64 65 /* 66 * Fast timeout routine for processing delayed acks 67 */ 68 void 69 tcp_fasttimo() 70 { 71 register struct inpcb *inp; 72 register struct tcpcb *tp; 73 int s = splnet(); 74 75 inp = tcb.inp_next; 76 if (inp) 77 for (; inp != &tcb; inp = inp->inp_next) 78 if ((tp = (struct tcpcb *)inp->inp_ppcb) && 79 (tp->t_flags & TF_DELACK)) { 80 tp->t_flags &= ~TF_DELACK; 81 tp->t_flags |= TF_ACKNOW; 82 tcpstat.tcps_delack++; 83 (void) tcp_output(tp); 84 } 85 splx(s); 86 } 87 88 /* 89 * Tcp protocol timeout routine called every 500 ms. 90 * Updates the timers in all active tcb's and 91 * causes finite state machine actions if timers expire. 92 */ 93 void 94 tcp_slowtimo() 95 { 96 register struct inpcb *ip, *ipnxt; 97 register struct tcpcb *tp; 98 int s = splnet(); 99 register int i; 100 101 tcp_maxidle = TCPTV_KEEPCNT * tcp_keepintvl; 102 /* 103 * Search through tcb's and update active timers. 104 */ 105 ip = tcb.inp_next; 106 if (ip == 0) { 107 splx(s); 108 return; 109 } 110 for (; ip != &tcb; ip = ipnxt) { 111 ipnxt = ip->inp_next; 112 tp = intotcpcb(ip); 113 if (tp == 0) 114 continue; 115 for (i = 0; i < TCPT_NTIMERS; i++) { 116 if (tp->t_timer[i] && --tp->t_timer[i] == 0) { 117 (void) tcp_usrreq(tp->t_inpcb->inp_socket, 118 PRU_SLOWTIMO, (struct mbuf *)0, 119 (struct mbuf *)i, (struct mbuf *)0); 120 if (ipnxt->inp_prev != ip) 121 goto tpgone; 122 } 123 } 124 tp->t_idle++; 125 if (tp->t_rtt) 126 tp->t_rtt++; 127 tpgone: 128 ; 129 } 130 tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */ 131 #ifdef TCP_COMPAT_42 132 if ((int)tcp_iss < 0) 133 tcp_iss = 0; /* XXX */ 134 #endif 135 splx(s); 136 } 137 138 /* 139 * Cancel all timers for TCP tp. 140 */ 141 void 142 tcp_canceltimers(tp) 143 struct tcpcb *tp; 144 { 145 register int i; 146 147 for (i = 0; i < TCPT_NTIMERS; i++) 148 tp->t_timer[i] = 0; 149 } 150 151 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 152 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 153 154 /* 155 * TCP timer processing. 156 */ 157 struct tcpcb * 158 tcp_timers(tp, timer) 159 register struct tcpcb *tp; 160 int timer; 161 { 162 register int rexmt; 163 164 switch (timer) { 165 166 /* 167 * 2 MSL timeout in shutdown went off. If we're closed but 168 * still waiting for peer to close and connection has been idle 169 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 170 * control block. Otherwise, check again in a bit. 171 */ 172 case TCPT_2MSL: 173 if (tp->t_state != TCPS_TIME_WAIT && 174 tp->t_idle <= tcp_maxidle) 175 tp->t_timer[TCPT_2MSL] = tcp_keepintvl; 176 else 177 tp = tcp_close(tp); 178 break; 179 180 /* 181 * Retransmission timer went off. Message has not 182 * been acked within retransmit interval. Back off 183 * to a longer retransmit interval and retransmit one segment. 184 */ 185 case TCPT_REXMT: 186 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 187 tp->t_rxtshift = TCP_MAXRXTSHIFT; 188 tcpstat.tcps_timeoutdrop++; 189 tp = tcp_drop(tp, tp->t_softerror ? 190 tp->t_softerror : ETIMEDOUT); 191 break; 192 } 193 tcpstat.tcps_rexmttimeo++; 194 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 195 TCPT_RANGESET(tp->t_rxtcur, rexmt, 196 tp->t_rttmin, TCPTV_REXMTMAX); 197 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 198 /* 199 * If losing, let the lower level know and try for 200 * a better route. Also, if we backed off this far, 201 * our srtt estimate is probably bogus. Clobber it 202 * so we'll take the next rtt measurement as our srtt; 203 * move the current srtt into rttvar to keep the current 204 * retransmit times until then. 205 */ 206 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 207 in_losing(tp->t_inpcb); 208 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 209 tp->t_srtt = 0; 210 } 211 tp->snd_nxt = tp->snd_una; 212 /* 213 * If timing a segment in this window, stop the timer. 214 */ 215 tp->t_rtt = 0; 216 /* 217 * Close the congestion window down to one segment 218 * (we'll open it by one segment for each ack we get). 219 * Since we probably have a window's worth of unacked 220 * data accumulated, this "slow start" keeps us from 221 * dumping all that data as back-to-back packets (which 222 * might overwhelm an intermediate gateway). 223 * 224 * There are two phases to the opening: Initially we 225 * open by one mss on each ack. This makes the window 226 * size increase exponentially with time. If the 227 * window is larger than the path can handle, this 228 * exponential growth results in dropped packet(s) 229 * almost immediately. To get more time between 230 * drops but still "push" the network to take advantage 231 * of improving conditions, we switch from exponential 232 * to linear window opening at some threshhold size. 233 * For a threshhold, we use half the current window 234 * size, truncated to a multiple of the mss. 235 * 236 * (the minimum cwnd that will give us exponential 237 * growth is 2 mss. We don't allow the threshhold 238 * to go below this.) 239 */ 240 { 241 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 242 if (win < 2) 243 win = 2; 244 tp->snd_cwnd = tp->t_maxseg; 245 tp->snd_ssthresh = win * tp->t_maxseg; 246 tp->t_dupacks = 0; 247 } 248 (void) tcp_output(tp); 249 break; 250 251 /* 252 * Persistance timer into zero window. 253 * Force a byte to be output, if possible. 254 */ 255 case TCPT_PERSIST: 256 tcpstat.tcps_persisttimeo++; 257 tcp_setpersist(tp); 258 tp->t_force = 1; 259 (void) tcp_output(tp); 260 tp->t_force = 0; 261 break; 262 263 /* 264 * Keep-alive timer went off; send something 265 * or drop connection if idle for too long. 266 */ 267 case TCPT_KEEP: 268 tcpstat.tcps_keeptimeo++; 269 if (tp->t_state < TCPS_ESTABLISHED) 270 goto dropit; 271 if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE && 272 tp->t_state <= TCPS_CLOSE_WAIT) { 273 if (tp->t_idle >= tcp_keepidle + tcp_maxidle) 274 goto dropit; 275 /* 276 * Send a packet designed to force a response 277 * if the peer is up and reachable: 278 * either an ACK if the connection is still alive, 279 * or an RST if the peer has closed the connection 280 * due to timeout or reboot. 281 * Using sequence number tp->snd_una-1 282 * causes the transmitted zero-length segment 283 * to lie outside the receive window; 284 * by the protocol spec, this requires the 285 * correspondent TCP to respond. 286 */ 287 tcpstat.tcps_keepprobe++; 288 #ifdef TCP_COMPAT_42 289 /* 290 * The keepalive packet must have nonzero length 291 * to get a 4.2 host to respond. 292 */ 293 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 294 tp->rcv_nxt - 1, tp->snd_una - 1, 0); 295 #else 296 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 297 tp->rcv_nxt, tp->snd_una - 1, 0); 298 #endif 299 tp->t_timer[TCPT_KEEP] = tcp_keepintvl; 300 } else 301 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 302 break; 303 dropit: 304 tcpstat.tcps_keepdrops++; 305 tp = tcp_drop(tp, ETIMEDOUT); 306 break; 307 } 308 return (tp); 309 } 310